1. Field of the Invention
This invention relates to methods of making tubular elements, and relates more particularly to the production of a tubular element defining an internal cavity and having at least one offset member extending from its inside surface into the internal cavity. Products of this nature can be of various sizes and shapes and made from different materials, but this invention is particularly concerned with a process for making a polymeric tubular element, such as a cylindrical tube, wherein the inwardly extending offset members are integrally formed with the peripheral wall.
One particular product of this nature is the hopper commonly found in commercially available bird feeders which comprises a cylindrical transparent plastic tube with a multiplicity of spaced feed ports or openings intermediate the top and bottom portions of the tube, commonly surrounded by a housing including a wire cage or the like to minimize access to the feed ports by squirrels and other small animals that tend to frighten off birds, quickly depleting the supply of bird food, and even destroying the hopper. The hoppers in such bird feeders are normally formed of a thermoplastic material such as polypropylene and include internally extending semicircular caps adapted to preclude the outflow of bird food from the hopper reservoir or internal cavity while permitting birds to access the bird food which flows by gravity to the feed ports under the cap members.
2. Description of the Related Art
The manufacture of tubular products with internally extending offset members, such as bird feeder hoppers having cap members adjacent each feed port extending into the hopper cavity, has caused significant difficulties. A simple and inexpensive method to manufacture a cylindrical element, which is the peripheral wall of the hopper, would be by injection molding of a thermoplastic polymer. However, the internally extending feed port cap members cannot be effectively formed integrally with the cylindrical peripheral wall because the internal molding element or core necessary to form the cap members would be impossible, or at the very least, practically impossible, to remove after the molding operation was complete. Therefore, heretofore the cap members have been molded as separate elements, independent of the peripheral wall of the hopper and subsequently secured internally of the hopper at each feed port, either adhesively or by a snap fit engagement of the cap member with the peripheral wall of the hopper. It is evident that such a process is time consuming, labor intensive, commercially inefficient and unnecessarily expensive.
With the foregoing in mind, it is a primary object of this invention to provide a method of making a tubular member, such as a bird feeder hopper, which enables the internally offset members, such as the feed port cap members, to be formed integrally with the peripheral wall by injection molding or the like, without the problems attendant to prior art attempts to integrally provide structures of this type.
A further object of this invention is the provision of a method for making a tubular member including such internally offset elements by first forming a sheet-like element, including a plurality of wall sections interconnected by integral hinges, with the offset members integrally formed with one or more of the wall sections, and then pivoting or folding the wall sections about the integral hinges to form a peripheral wall, and interconnecting the mating edges of the sheet-like element to form the tubular member.
Yet another object of this invention is the provision of tubular products, such as bird feeder hoppers of the type described, with integrally formed, internally offset members, such as the semicircular cap members commonly found at each feed port on a bird feeder hopper to protect against loss of bird food from the internal cavity formed by the peripheral wall through the feed ports.
Another object of this invention is the provision of an injection molding technique for forming a sheet-like element with a plurality of wall sections each having a preselected thickness, the wall sections being integrally interconnected to each other by portions which are thinner than the thickness of the wall sections they interconnect and thereby form integral hinges, to enable the wall sections to be bent or pivoted about the hinges to produce the tubular product.
A still further object of this invention is the provision of integral locking members on the edge portions of the end wall sections of such sheet-like elements so that when the wall sections are folded about their integral hinges to produce the peripheral wall, the complementary locking members can be interengaged to retain the sheet-like member in its tubular form without the need for extraneous tools. Alternatively or additionally, the end sections of the sheet-like member may be interconnected during the manufacturing process by heat sealing the edge portions to each other.
More generally, this invention is directed to a method of making a tubular member, such as a bird feeder hopper, and the products so produced, in a simple, inexpensive and commercially efficient manner.